Abstract

A study comparing Jersey (J) and Friesian (F) cows in early (EL), mid (ML) and late (LL) lactation and offered either ad libitumpasture (P) or restricted pasture allowance + a concentrate (PC) was conducted. Breeds were grazed at a similar live weight (LWT)/ha (1340 and 1850 kg LWT/ha for P and PC respectively). F cows produced 10% more MS/cow/day than J cows. DM intake (DMI) on P was 13.6 kg DM/cow/day for F and 11.3 kg DM/cow/day for J cows but if expressed at constant LWT, J consumed more than F cows (30.3 versus 28.0 + 0.8 g DMI/kg LWT). During EL, J cows gained less live weight than F cows but in LL the reverse occurred. An interaction between breed and stage of lactation also occurred for the conversion efficiency of pasture DM to milkfat, protein, casein and MS. For the yield of milkfat, protein and casein J cows in EL were more efficient than F cows but in LL no breed effect on the conversion efficiency of pasture to these components occurred. The difference between breeds in partitioning feed to milk solids and liveweight gain at different stages of lactation suggests different management opportunities for each breed to more efficiently convert pasture to MS.

NA, Thomson, JK Kay, and MO Bryant

Proceedings of the New Zealand Society of Animal Production, Volume 61, Christchurch, 213-216, 2001